Corn Ethanol Industry Research Articles

Merging remote sensing data and national agricultural statistics to model change in irrigated agriculture

Over 22 million hectares (ha) of U.S. croplands are irrigated. Irrigation is an intensified agricultural land use that increases crop yields and the practice affects water and energy cycles at, above, and below the land surface. Until recently, there has been a scarcity of geospatially detailed information about irrigation that is comprehensive, consistent, and timely to support studies tying agricultural land use change to aquifer water use and other factors. This study shows evidence for a recent overall net expansion of 522 thousand ha across the U.S. (2.33%) and 519 thousand ha (8.7%) in irrigated cropped area across the High Plains Aquifer (HPA) from 2002 to 2007. In fact, over 97% of the net national expansion in irrigated agriculture overlays the HPA. We employed a modeling approach implemented at two time intervals (2002 and 2007) for mapping irrigated agriculture across the conterminous U.S. (CONUS). We utilized U.S. Department of Agriculture (USDA) county statistics, satellite imagery, and a national land cover map in the model. The model output, called the Moderate Resolution Imaging Spectroradiometer (MODIS) Irrigated Agriculture Dataset for the U.S. (MIrAD-US), was then used to reveal relatively detailed spatial patterns of irrigation change across the nation and the HPA. Causes for the irrigation increase in the HPA are complex, but factors include crop commodity price increases, the corn ethanol industry, and government policies related to water use. Impacts of more irrigation may include shifts in local and regional climate, further groundwater depletion, and increasing crop yields and farm income.

Understanding the evolution of environmental and energy performance of the US corn ethanol industry: evaluation of selected metrics

AbstractThroughout the past two decades, numerous studies characterized the greenhouse gas (GHG) emissions and net energy balance of corn ethanol production in the USA. A wide range of reported values resulted from differences in the vintage of the data used to evaluate the ethanol conversion technology and the agricultural practices of corn production, which evolved substantially during the rapid growth phase of the industry. Methodological differences in life cycle assessments also caused the reported values to vary widely. With corn dry mills growing from 30% of total installed ethanol production capacity in 1990 to 80–90% from 2006 to 2011, we document the evolution of this industry using vintage‐specific data to analyze selected energy and environmental metrics, including GHG emissions, fossil energy use, direct land use, and GHG emissions reduction per hectare of land harvested for ethanol production. Our estimates indicate that production and use of corn ethanol emitted 44% fewer GHG emissions, consumed 54% less fossil energy and required 44% less land in 2010 compared to 1990 (on a life cycle basis). Our review and analysis point to strategies for reducing the carbon footprint of the corn dry mill industry by building on the progress already achieved. Using biomass (e.g. residues from corn production) for process heat or combined heat and power is one such strategy. Additional environmental benefits are projected from the adoption of integrated gasification combined cycle technology (using corn residues), which leads to energy‐self‐sufficient mills or net electricity producers depending on the power system configuration. © 2013 Society of Chemical Industry and John Wiley & Sons, Ltd

Fundamental studies on water-washing of the corn ethanol coproduct (DDGS) and its characterization for biocomposite applications

Distiller's dried grains with solubles (DDGS), the main coproduct in the dry mill corn ethanol industry, is finding its way toward a reinforcing filler in polymeric composite applications. In such a journey, thermal stability of DDGS is a critical factor affecting both temperature window of DDGS melt-compounding with polymers and the properties of the final biocomposite material. In this study, DDGS thermal stability was enhanced by washing with water and then used to fabricate biocomposites with Poly(1, 4-butanediol succinate) (PBS). The thermal degradation of DDGS, before and after washing, was studied with thermogravimetric (TG) and derivative thermogravimetric (DTG) analyses, showing up to 50 °C improvement in degradation onset temperature of DDGS after washing. Also, the degradation activation energies for water-washed DDGS were smaller than the respective values for as-received DDGS. Compositional analysis and infrared spectroscopy showed that the water-washed DDGS was higher in protein and fiber content compared to as-received DDGS. As a result of improved thermal stability of DDGS after water-washing, the DDGS burning during melt processing was highly prevented and the biocomposites processed at 160 °C and 190 °C showed constant tensile properties. On the other hand, for as-received DDGS biocomposites the tensile properties decreased as the processing temperature increased. Moreover, the increased fiber content of DDGS after water-washing resulted in biocomposites with higher tensile strength and modulus compared to as-received DDGS biocomposites.

Continuous SSCF of AFEX™ pretreated corn stover for enhanced ethanol productivity using commercial enzymes and Saccharomyces cerevisiae 424A (LNH‐ST)

High productivity processes are critical for commercial production of cellulosic ethanol. One high productivity process-continuous hydrolysis and fermentation-has been applied in corn ethanol industry. However, little research related to this process has been conducted on cellulosic ethanol production. Here, we report and compare the kinetics of both batch SHF (separate hydrolysis and co-fermentation) and SSCF (simultaneous saccharification and co-fermentation) of AFEX™ (Ammonia Fiber Expansion) pretreated corn stover (AFEX™-CS). Subsequently, we designed a SSCF process to evaluate continuous hydrolysis and fermentation performance on AFEX™-CS in a series of continuous stirred tank reactors (CSTRs). Based on similar sugar to ethanol conversions (around 80% glucose-to-ethanol conversion and 47% xylose-to-ethanol conversion), the overall process ethanol productivity for continuous SSCF was 2.3- and 1.8-fold higher than batch SHF and SSCF, respectively. Slow xylose fermentation and high concentrations of xylose oligomers were the major factors limiting further enhancement of productivity.

The Agricultural Ethics of Biofuels: The Food vs. Fuel Debate

Plant-based transportation fuels were the focus of extended criticism in the press, especially during 2008 when a portion of the blame for a spike in global food prices was associated with growth of the United States’ corn ethanol industry. The critique is based on an unsophisticated portrayal of the ethical issues at stake in the food security implications of biofuel. Three ethical critiques can be leveled at the food vs. fuel debate. First, although market drivers of biofuels indeed skew consumption of agricultural grains, this is not a problem that is unique to biofuels. Second, the critique does not reflect an adequate understanding of the way that rising food prices and changes in agricultural technology affect the food security of the poorest people. Third, although rising food prices could be beneficial to poor farm producers among the world’s poor, it is unlikely that benefits will materialize in the absence of concerted programs to deliberately select biofuel development strategies that are targeted to strengthen food security for poor and small-holding producers. An adequate agricultural ethics for biofuels will require commitment by both private and public sector biofuel developers to ensure that potentially positive attributes of biofuel development are realized.

Biodegradable green composites from bioethanol co-product and poly(butylene adipate-co-terephthalate)

This work summarizes the development of green composites from distillers dried grains with solubles (DDGS), a major co-product of the corn ethanol industry, and poly (butylene adipate-co-terephthalate), PBAT. The composites were fabricated using a twin-screw micro extruder with micro injection molding. The DDGS was pretreated, yielding a noticeable improvement in the degradation onset temperature of DDGS from 140 to 240°C, which was shown by thermogravimetric analysis (TGA). The composite fabricated with pretreated DDGS showed better mechanical and thermal properties compared to the composite with non-treated DDGS. TGA analysis showed that the maximum degradation rate shifted slightly to lower values with the increase of filler content. Differential scanning calorimetry (DSC) analysis showed that the glass transition temperature (Tg) of the matrix increased slightly with an increase in filler content, indicating that filler did not lead to significant change in crystalline structure. The biodegradability study showed that, PBAT/treated DDGS composite was found to be the most bio-susceptible material, being totally biodegraded. This suggests that DDGS domains were preferentially attacked by microorganisms, and increased the percentage of biodegradation. All composite materials showed a degree of biodegradation similar to the biodegradation rate of DDGS and cellulose. This study showed that the incorporation of DDGS into a PBAT matrix can produce green composites with enhanced biodegradability.

Phosphorus Flow and Characterization in Dry‐Grind Corn Ethanol Plants

Both the high phosphorus (P) content and P bioavailability of the animal feed coproducts of the corn-ethanol industry could potentially contribute to increased manure and soil P levels and associated environmental issues (e.g., eutrophication). Therefore, a detailed modeling of total P mass flow to the coproducts (i.e., dry distillers grains with solubles, DDGS) was performed. Distribution of P between inorganic P and phytase-hydrolyzable P forms was quantified for selected coproducts (thin stillage, DDGS, modified DDGS [mDDGS]). The P mass balance indicated that although corn is the major P contributor to the coproducts (80.2%), a substantial portion (19.4%) comes from yeast addition. Of the two components constituting DDGS, wet distillers grains and condensed solubles, the latter contributes to only one-third of the mass but, importantly, yields 70.9% of P. The phytase enzyme used, , was very effective in hydrolyzing the nonorthophosphate P components of thin stillage, DDGS and mDDGS. Our results would help track P movement during various dry-grind processing steps and formulate strategies for phytase enzyme supplementation to various postfermentation coproducts from corn-ethanol plants.

Environmental efficiency among corn ethanol plants

Economic viability of the US corn ethanol industry depends on prices, technical and economic efficiency of plants and the extent of policy support. Public policy support is tied to the environmental efficiency of plants measured as their impact on emissions of greenhouse gases. This study evaluates the environmental efficiency of seven recently constructed ethanol plants in the North Central region of the US, using nonparametric data envelopment analysis (DEA). The minimum feasible level of GHG emissions per unit of ethanol is calculated for each plant and this level is decomposed into its technical and allocative sources. Results show that, on average, plants in our sample may be able to reduce GHG emissions by a maximum of 6% or by 2.94 Gg per quarter. Input and output allocations that maximize returns over operating costs (ROOC) are also found based on observed prices. The environmentally efficient allocation, the ROOC-maximizing allocation, and the observed allocation for each plant are combined to calculate economic (shadow) cost of reducing greenhouse gas emissions. These shadow costs gauge the extent to which there is a trade off or a complementarity between environmental and economic targets. Results reveal that, at current activity levels, plants may have room for simultaneous improvement of environmental efficiency and economic profitability.

Biofuels and agriculture: a past perspective and uncertain future

The US corn ethanol industry has grown from virtually nothing in the early 1980s to over 14 billion gallons in 2011. Subsidies have been an important impetus for the industry, and they have existed in one form or another throughout the life of the industry. This paper provides (1) a brief look at the history of the linkages between energy and agriculture and how they have changed with biofuels; (2) a review of some of the major impacts of the US corn ethanol program; and (3) analysis of prospective impacts of cellulosic biofuels. There is no doubt that biofuels have brought about a new era for global agriculture. Historically, the prices of agricultural and energy products moved in response to supply and demand factors relevant to each market, but moved largely independent of one another. Corn ethanol has changed that, and today there is a link between crude oil and corn that is driven by the demand side. Since agricultural commodity prices are linked both on the demand and supply sides, the corn–crude oil link spills over to other agricultural commodities as well. Development of cellulosic biofuels has been much slower than hoped. The feedstocks are more expensive than initially believed. Conversion technologies remain uncertain and expensive. There are many uncertainties through the cellulosic supply chain, and government policy remains uncertain as well. Thus, the future of the cellulosic biofuels industry is, at this point, an open question.

Explaining the reductions in US corn ethanol processing costs: Testing competing hypotheses

The processing costs of US corn ethanol have declined by 45% since 1983 as production volumes have increased seventeen-fold. We investigate the role of various factors that could explain this, including economies of scale, cumulative experience, induced innovation in response to rising input prices, an autonomous technological change, and trade induced competition from imported ethanol. Using data on dry-mill ethanol processing costs over the 1983–2005 period, we find evidence to show that US corn ethanol production exhibited decreasing returns to scale, that learning by doing played an important role in reducing these processing costs with a learning rate of 0.25, and that sugarcane ethanol imports contributed to making the corn ethanol industry more competitive. Other factors such as the rising prices of energy and labor did induce lower processing costs, but the effect is not statistically significant. The inclusion of these competing explanations for the reduction in processing costs of US corn ethanol lead to a significantly higher learning rate than otherwise, and this learning rate is found to be robust across specifications.

PHA productivity and yield of Ralstonia eutropha when intermittently or continuously fed a mixture of short chain fatty acids.

The research described in this present study was part of a larger effort focused on developing a dual substrate, dual fermentation process to produce Polyhydroxyalkanoate (PHA). The focus of this study was developing and optimizing a strategy for feeding a mixture of SCFAs (simulated ARF) and maximizing PHA production in a cost-effective way. Three different feeding strategies were examined in this study. The substrate evaluated in this study for the growth phase of R. eutropha was condensed corn solubles, a low-value byproduct of the dry-mill, corn ethanol industry. The culture was grown to high cell densities in nitrogen-supplemented condensed corn solubles media in 5 L bioreactors. The overall growth rate of R. eutropha was 0.2 h−1. The 20 mL ARF feeding every 3 h from 48 to 109 h strategy gave the best results in terms of PHA production. PHA productivity (0.0697 g L−1 h−1), PHA concentration (8.37 g L−1), and PHA content (39.52%) were the highest when ARF was fed every 3 h for 61 h. This study proved that condensed corn solubles can be potentially used as a growth medium to boost PHA production by R. eutropha thus reducing the overall cost of biopolymer production.

Glass transition behavior of corn distillers dried grains with solubles (DDGS)

Distillers dried grains with solubles (DDGS), a major co-product from the corn ethanol industry, has high feed value for its chemical composition. The ratio of wet distillers grains (WDG) and condensed distillers solubles (CDS) added during the production process determines the chemical composition of DDGS. Effect of changing this ratio and the influence of moisture content on glass transition behavior of DDGS was studied. Five prediction models were evaluated to explain the glass transition of DDGS. The mixed trends in the result indicated the complex behavior of DDGS particles and revealed that both moisture content and chemical composition impact the glass transition behavior of DDGS. Onset glass transition temperature ranged from 20 to 30 °C depending on the chemical composition. Kwei equation predictions were better than the predictions by Gordon–Taylor equation. The glass transition temperature of DDGS can be mathematically explained by combining the moisture content and chemical components protein, fiber, glycerol, and sugar percent. The artificial neural network (ANN) model gave a better prediction of onset and midpoint glass transition temperature of DDGS and this might be due to the accurate mapping of the interaction between chemical components.

Biodegradable Green Composites from Distiller's Dried Grains with Solubles (DDGS) and a Polyhydroxy(butyrate‐co‐valerate) (PHBV)‐Based Bioplastic

AbstractBiodegradable green composites from distiller's dried grains with solubles (DDGS), a major coproduct of the corn ethanol industry, and a polyhydroxy(butyrate‐co‐valerate) (PHBV)‐based bioplastic were successfully produced. Green surface treatment of DDGS was performed and thermogravimetric analysis showed noticeable improvement in the degradation onset temperature of DDGS from 140 to 235 °C; this was a key point during melt processing of the composite. Utilizing compatibilizer improved the adhesion between DDGS and the matrix, which was observed by scanning electron microscopy. The green composite containing treated and compatibilized DDGS showed an enhanced modulus (by about 28% from 1.77 to 2.26 GPa) and an improved heat deflection temperature (by about 21% from 109 to 132 °C) compared to the polymeric matrix, while having tensile and flexural strengths equal to or greater than the respective properties of the matrix.magnified image

A resilience perspective on biofuel production

The recent investment boom and collapse of the corn ethanol industry calls into question the long-term sustainability of traditional approaches to biofuel technologies. Compared with petroleum-based transportation fuels, biofuel production systems are more closely connected to complex and variable natural systems. Especially as biofeedstock production itself becomes more independent of fossil fuel-based supports, stochasticity will become an increasingly important, inherent feature of biofuel feedstock production systems. Accordingly, a fundamental change in design philosophy is necessary to ensure the long-term viability of the biofuels industry. To respond effectively to unexpected disruptions, the new approach will require systems to be designed for resilience (indicated by diversity, efficiency, cohesion, and adaptability) rather than more narrowly defined measures of efficiency. This paper addresses important concepts in the design of coupled engineering-ecological systems (resistance, resilience, adaptability, and transformability) and examines biofuel conversion technologies from a resilience perspective. Conversion technologies that can accommodate multiple feedstocks and final products are suggested to enhance the diversity and flexibility of the entire industry.

The Impact of Ethanol Plants on Surrounding Farmland Values: A Case Study

The expansion of the corn ethanol industry after 2003 increased corn prices throughout the United States, and, in some cases, prices were shown to be higher with proximity to individual ethanol plants. This leads to the hypothesis that the value of farmland in close proximity to ethanol plants is higher than comparable farmland located farther away. This hypothesis was explored by examining the sale of 961 farmland parcels during 2004–2008, in the vicinity of two corn ethanol plants in northeastern Nebraska. Hedonic models including land characteristics as well as spatial and plant proximity measures failed to show support for the hypothesis.

Operating Characteristics of a High-Efficiency Pilot Scale Corn Distillers Grains Dryer

The rapidly expanding U.S. corn ethanol industry produces huge quantities of wet distillers grains and about 70% of this material is dried to 10% moisture. Drying this material requires about one-third of the energy used to operate a dry-grind corn ethanol plant. Tri-Phase Drying Technologies of Norwalk, Iowa has developed a rotary drum dryer which reclaims energy from the exhaust air stream. The objective of this research was to determine the energy requirement of the Tri-Phase dryer by pilot scale drying tests with wet distillers grains. Multiple tests of the pilot-scale dryer showed an energy input requirement of about 2890 kJ/kg (846 Btu/lb) of water removed when drying wet distillers grains from about 28% to 24% moisture. This is less than half the energy usually required for a drum dryer or a grain dryer. Use of this dryer design, scaled up to dry distillers grains at ethanol plants, has the potential for large energy savings for the corn ethanol industry.

Fermentation of biomass sugars to ethanol using native industrial yeast strains

In this paper, the feasibility of a technology for fermenting sugar mixtures representative of cellulosic biomass hydrolyzates with native industrial yeast strains is demonstrated. This paper explores the isomerization of xylose to xylulose using a bi-layered enzyme pellet system capable of sustaining a micro-environmental pH gradient. This ability allows for considerable flexibility in conducting the isomerization and fermentation steps. With this method, the isomerization and fermentation could be conducted sequentially, in fed-batch, or simultaneously to maximize utilization of both C5 and C6 sugars and ethanol yield. This system takes advantage of a pH-dependent complexation of xylulose with a supplemented additive to achieve up to 86% isomerization of xylose at fermentation conditions. Commercially-proven Saccharomyces cerevisiae strains from the corn-ethanol industry were used and shown to be very effective in implementation of the technology for ethanol production.

The integration of energy and agricultural markets

AbstractThis article addresses the evolving links between energy and agricultural markets. Prior to 2005, there was little correlation between energy and agricultural commodity prices. In 2006–2008, with the ethanol boom in the United States, there emerged a strong link between crude oil, gasoline, and corn prices. There was little link between ethanol and corn. However, in late 2008 and 2009, the markets changed as ethanol production came under severe economic pressure and 2 billion out of 12 billion gallons of capacity shut down. During this period ethanol became priced more on corn, as the breakeven corn price helped drive the ethanol market. This article explores the drivers in these markets as well as other major issues facing the corn ethanol industry in the United States such as the blend wall. The article concludes with a review of prospects of a future cellulosic biofuels industry.

Impacts of the corn grain ethanol industry on the United States agricultural sector

The growth in ethanol production from corn starch in the United States has increased concerns about soil erosion, fertilizer and pesticide pollution, and greenhouse gas emission problems with expanded corn production. This study evaluated the effects of increased corn production on agricultural land use, tillage intensity, and the environment at the regional and national levels for the United States. The Policy Analysis System (POLYSYS) agricultural policy simulation model was used to estimate the impacts of a growing corn ethanol industry. The analysis provided a comparison for the 2007 through 2016 period of the projected impacts of ethanol production rising from 32.5 million kL y−1 (8.6 billion gal yr−1) in 2007 to 45.3, 60.4, and 67.9 million kL y−1 (12, 16, or 18 billion gal yr−1) by 2016. For each ethanol production scenario, POLYSYS was used to simulate crop production under alternative tillage practices for 305 growing regions in the United States, livestock production, crop and livestock demands, and national agricultural income. In addition, POLYSYS was used to simulate changes in water-induced soil erosion and sedimentation, carbon emissions, carbon sequestration, chemical expenditures, and fertilizer expenditures for each growing region.

Feeding value of glycerol as a replacement for corn grain in rations fed to lactating dairy cows

Growth of the corn ethanol industry has created a need for alternatives to corn for lactating dairy cows. Concurrent expansion in soydiesel production is expected to increase availability and promote favorable pricing for glycerol, a primary co-product material. The objective of this study was to determine the feeding value of glycerol as a replacement for corn in diets fed to lactating dairy cattle. Sixty lactating Holstein cows housed in individual tie stalls were fed a base diet consisting of corn silage, legume forages, corn grain, soyhulls, roasted soybeans, and protein supplements. After a 2-wk acclimation period, cows were fed diets containing 0, 5, 10, or 15% refined glycerol for 56 d. Cows were milked twice daily and weekly milk samples were collected. Milk production was 36.3, 37.2, 37.9, and 36.2±1.6kg/d and feed intake was 23.8, 24.6, 24.8, and 24.0±0.7kg/d for 0, 5, 10, and 15% glycerol treatments, respectively, and did not differ except for a modest reduction in feed intake during the first 7 d of the trial for 15% glycerol (treatment×time effect). Milk composition was not altered by glycerol feeding except that milk urea nitrogen was decreased from 12.5±0.4 to 10.2±0.4mg/dL with glycerol addition. Cows fed diets containing 10 and 15% glycerol gained more weight than those fed rations containing 0 or 5% glycerol but body condition scores did not differ with glycerol feeding. The data indicate that glycerol is a suitable replacement for corn grain in diets for lactating dairy cattle and that it may be included in rations to a level of at least 15% of dry matter without adverse effects on milk production or milk composition.